A) can èëè may
1. Speak louder, I … not hear you.
2. … I trouble you for a moment?
3. … I smoke here?
4. People … not see well in the evening.
5. She … play tennis well when she was young.
B) must/need.
1. You … use a computer in your work.
2. They … much time to finish a project.
3. She … take this medicine regularly.
4. You …. not go the conference. We have already sent Jack there.
5. It … be his car.